Method and apparatus for forming dental prosthesis

ABSTRACT

Method and apparatus for forming permanent dental prosthesis (i.e., dental bridges) in situ, meaning that the bridge is formed and secured in place directly in the mouth of the patient without the necessity for making impressions, casting models and other processes normally required to form a bridge. This is accomplished in accordance with the principal embodiment of the invention by (1) drilling cavities in two teeth on either side of a space to be occupied by a bridge; (2) inserting into the cavities the opposite ends of a metallic bar; (3) securing the ends of the bar in place within the cavities with a filling material placed in the cavities; (4) inserting a filling material, preferably an unhardened resin-bonded quartz composite in paste form, into one or more hollow tooth molds; (5) forcing the tooth molds containing the unhardened pastelike filling material over the bar and permitting the filling material to harden to form a solid tooth structure which is bonded to the aforesaid bar; and (6) removing the tooth mold or molds from the thus-hardened tooth structure, the thus-formed teeth being held in the mouth by the aforesaid bar anchored to living teeth on either side of the space occupied by the bridge. While in most cases the bar will be secured at its opposite ends within two cavities, it is also within the purview of the invention to secure one end of the bar only within a cavity drilled in one tooth, the prosthesis being supported in cantilever beam fashion. This is particularly useful in forming teeth at the front of the mouth (e.g., a lateral incisor supported on a cantilever bar secured at one end to a cuspid).

United States Patent Karageorge [54] METHOD AND APPARATUS FOR FORMING DENTAL PROSTHESIS [72] Inventor: Louis J. Karageorge, 518 St. James Place,

Pittsburgh, Pa. 15232 221 Filed: Apr. 7, 1970 21 Appl.No.: 26,329

Primary ExaminerRobert Peshock Attorney-Brown, Murray, Flick & Peckham [57] ABSTRACT Method and apparatus for forming permanent dental prosthesis (i.e., dental bridges) in situ, meaning that the bridge is 1 Feb. 15, 1972 formed and secured in place directly in the mouth of the patient without the necessity for making impressions, casting models and other processes normally required to form a bridge. This is accomplished in accordance with the principal embodiment of the invention by (l) drilling cavities in two teeth on either side of a space to be occupied by a bridge; (2) inserting into the cavities the opposite ends of a metallic bar; (3) securing the ends of the bar in place within the cavities with a filling material placed in the cavities; (4) inserting a filling material, preferably an unhardened resin-bonded quartz composite in paste form, into one or more hollow tooth molds; (5) forcing the tooth molds containing the unhardened pastelike filling material over the bar and permitting the filling material to harden to form a solid tooth structure which is bonded to the aforesaid bar; and (6) removing the tooth mold or molds from the thus-hardened tooth structure, the thusformed teeth being held in the mouth by the aforesaid bar anchored to living teeth on either side of the space occupied by the bridge. While in most cases the bar will be secured at its opposite ends within two cavities, it is also within the purview of the invention to secure one end of the bar only within a cavity drilled in one tooth, the prosthesis being supported in cantilever beam fashion. This is particularly useful in forming teeth at the front of the mouth (e.g., a lateral incisor supported on a cantilever bar secured at one end to a cuspid).

13 Claims, 9 Drawing Figures PATENTEOFEBIS I972 3,641,670

uw/va TEETH T R DEAD, TREATED TEETH A I forneys METHOD AND APPARATUS FOR F ORMING'DENTAL PROSTI-IESIS BACKGROUND OF THE INVENTION Dental bridges according to the prior art are normally classified as permanent or removable and are formed from a fired ceramic material over a metallic matrix or an acrylic plastic or the like. Permanent bridges are normally of the fired ceramic type and are fixed in the mouth by securing caps to teeth on either side of the space to be occupied by the bridge, these caps being integrally connected to an artificial tooth or teeth, also formed from porcelain, which occupy the former gap extending along the gum. Removable bridges, on the other hand, are secured to adjacent living teeth on either side of a gap by clips such that the bridge may be removed for cleaning.

In either case, whether the bridge be permanent or removable, prior art processes for forming bridges are time-consuming, expensive and involve a number of visits by the patient to the dentist. The initial step in theprocess is to form a wax, rubber or similar impression of the gum and a number of teeth on either side of a gap to be occupied by'the bridge. A technician, having received from the dentist the impression of the teeth, then pours dental stone into the impression to form a model of the patients gum and teeth. From this model, a bridge is constructed which, in the case of porcelain bridges, involves investment casting of metal matrices, sculpturing of unfired ceramic material around the metal matrix, and firing of the ceramic. The completed bridge, if it is permanent, must then be cemented into the patients mouth.

Thus, prior art methods for forming dental prostheses such as bridges always involved the making of a model of a portion of a patients dentures, followed by a tedious and time-consumingprocedure in forming the bridge itself and securing it in place.

SUMMARY OF THE INVENTION In accordance with the present invention, a method and apparatus are provided for forming a permanent dental bridge in situ, without requiring the formation of a model formed from dental stone. The entire bridge canbe formed in the mouth of the patient in one setting and ordinarily in less than 2 hours. This is accomplished in accordance with the invention by initially drilling a'distal cavity in one of the teeth adjacent a gap to be occupied by a bridge and a mesial cavity in the tooth on the other side of the gap. As will be seen, however, in certain cases only one cavity need be drilled. These teeth may be whole, living or dead teeth or previously capped teeth. Inserted into the cavities are the opposite ends of a metallic bar, preferably containing, as essential alloying constituents, platinum, cobalt and chromium, This bar must have adequate corrosion resistance; and at the same time must have relatively high bending strength. The bar is preferably provided with crossbars, knurls, or some other type of projection which extends radially outwardly from the bar so as to provide a means for securing and anchoring the ends of the bar within the teeth on either side of the bridge as well as the false teeth forming the bridge itself without permitting rotation of the bar or the false teeth formed thereon.

After the ends of the bar are inserted into the cavities drilled in the teeth on either side of the gap to be filled by the bridge, the cavities are filled with a filling material which preferably comprises a resin-bonded crystal quartz powder. The filling material is inserted into the cavities as a paste which will harden in approximately 1% minutes.

At this juncture, therefore, the bar has been secured to the living or dead teeth on either side of the space to be occupied by the bridge. In order to form the false teeth forming the bridge, a tooth form, of the type used to form plastic crowns, is cut away such that it will fit over the bar spanning the gap to be occupied by the bridge. The form is then filled with the aforesaid resin-bonded rock quartz filling material and the form, containing the filling material, pushed down over the bar spanning the gap to be occupied by the bridge. This process is repeated a second or even third time, depending upon how many teeth are missing from the space to be occupied by the bridge. The patient is then told to bite down-on the plastic form such that a good bite is achieved. Within 5 minutes, the plastic forms can be removed from the nowhardened tooth forms and the bridge is completed.

It will be understood, of course, that if the bar is to be supported on one tooth only in cantilever beam fashion. the process is the same except that it is necessary to drill one cavity only.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specification, and in which:

FIG. 1 is a top view of the lower right half of the gum showing the dentures therein with the first molar'missing and also showing the manner in which the second bicuspid and second molar are drilled in preparation for forming a bridge;

FIG. 2 is a side perspective view of the second molar and second bicuspid as drilled in preparation for receiving a spanning bar;

FIG. 3 shows the spanning bar in position within the previ ously drilled cavities;

FIG. 4 illustrates the manner in which a plastic tooth form is fitted over the spanning bar in preparation for receipt of a molded tooth form;

FIG. 5 shows the manner in which the tooth form of FIG. 4, now filled with a hardenable filling material, is forced downwardly over the spanning bar and into place.

FIGS. 6-8 illustrate alternative embodiments of the spanning bar of the invention; and

FIG. 9 illustrates another embodiment of the invention wherein the bar is supported at one end only in cantilever beam fashion.

With reference now to the drawings, and particularly to FIG. 1, the lower right-hand portion of the gum 10 is shown having in place the natural teeth excepting the first molar. The teeth include the central incisor 12, the lateral incisor 14, the cuspid 16, the first bicuspid 18, the second bicuspid 20 and the second molar 22. As mentioned above, the first molar, which normally occupies the space 24, is missing.

In accordance with the present invention, the initial step in forming a bridge is to drill distal and mesial cavities 26 and 28 .in the second bicuspid 20 and second molar 22, respectively.

These are perhapsbetter shown in FIG. 2. After the cavities 26 and 28 are thus drilled, a spanning bar 30 (FIG. 2) is inserted down into the two cavities 26 and 28. Preferably, the bar 30 is provided with crossbars 32 which, as will hereinafter be explained, prevent turning of the spanning bar within the cavities 26 and 28 and also prevent rotation of a formed tooth which is secured to the bar 30 and fits into the space between the teeth 20 and 22. Instead of having the crossbars 32, however, the spanning bar 30 may be provided with other types of radial projections, hereinafter described, which serve to prevent rotation of the bar and the tooth or teeth formed thereon once the bridge is in place.

The cavities 26 and 28 may be drilled regardless of whether there are previous cavities existing in the teeth, or whether there are caps on the living teeth. If, after drilling the cavities, the teeth have exposures of the pulp, a pinch of cotton is dipped and saturated with the patients own saliva (which contains antigens) and the cotton then dipped in slaked lime and placed directly on the blood exposure. Upon covering the blood exposure, the proper cement lining is then placed over the slaked lime.

The spanning bar 30 may, for example, have a cross section of 1 square millimeter with one-half millimeter crossbars 32 welded thereto or integrally cast therewith. It is of sufficient length to span the space between the two teeth 20 and 22 with its ends extending well into the cavities 26 and 28. The crossbars 32 may extend either vertically or horizontally, depending upon the manner in which the spanning bar fits into the cavities 26 and 28.

After the spanning bar 30 is fitted into the cavities 26 and 28 as shown in FIG. 3, it is anchored to the two teeth 20 and 22 by filling the cavities 26 and 28 with a suitable filling material 31. The filling material 31 is preferably of the type sold by Johnson and Johnson of New Brunswick, New Jersey under the trademark ADAPTIC. It comprises a resin-bonded quartz composite (i.e., resin-bonded crystal quartz powder) which retains much of the original clarity and toughness of crystal quartz. It has a smooth glossy surface with excellent stain resistance and it is ordinarily indistinguishable from the surrounding tooth structure. The filling material is prepared by mixing two pastes to form a filling paste which subsequently hardens into a rocklike mass in approximately 1% minutes. After the spanning bar 30 is secured in place as shown in FIG. 3, the fillings in the cavities 26 and 28 are trimmed and sandpapered until they assume the appearance of normal enamel.

As shown in FIG. 4, a clear polyester tooth form 34, in this case a tooth form for the first molar, is cut away at 36 and 38 such that it will fit down over the spanning bridge bar 30 with the openings 36 and 38 and permitting the form to fit down into snug-abutting relationship with the gum on all four sides. The clear form 34 is then pierced as at 40 and 42 to permit the escape of air when the filling material is subsequently charged into the form 34.

A new mix ofa resin-bonded quartz composite in paste form is then made and is placed over the spanning bar 30. At the same time, the form 34 is filled with the paste and placed over the spanning bar 30. The patient is then told to bite in centric (swallow and bite) and stay in centric for minutes. By this time, the resin-bonded quartz composite has hardened into a rocklike mass such that the clear polyester form 34 can be cut away from the now-formed molar 43 and removed to produce the completed bridge shown in FIG. 5. Any excess of the resinbonded quartz composite is removed from around the bottom or sides ofthe form 34 before crystallization.

In FIG. 6, another embodiment of the spanning bar 30 is shown which is provided with both horizontally extending and vertically extending crossbars 44. Again, in FIG. 7, another embodiment of the spanning bar 30 is shown which is knurled and which, when embedded in the resin-bonded quartz composite, will prevent the bar from turning as well as the formed tooth 43 fitted over the bar 30 in the space between teeth and 22, for example. The essential requirement of the bar 30 is that it have some type of radially extending projections which will become embedded in the resin-bonded quartz composite and prevent the bar and/or the false tooth from rotating. In FIG. 8, still another embodiment of the bar 30 is shown having projections 46 extending radially outwardly therefrom. The cross-sectional area of the bar 30 may be 1.5 square millimeters and that of the projections 46 0.75 square millimeter.

As was mentioned above, the bar 30 and the projections thereon should be formed from a metal or alloy which has high-corrosion resistance and at the same time has sufficient bending strength. Preferably, the alloy contains, as essential constituents, platinum, cobalt and chromium. The following alloys have been found suitable for the bar 30:

In general, therefore, it can be said that the alloy should contain from 20-40 percent, from 10-35 percent cobalt and from 10-40 percent chromium; although any metal or other material can be used which has good corrosion resistance and sufficient bending strength.

In FIG. 7, an alternative embodiment of the invention is shown for replacing a lateral incisor with a dental prosthesis. It is, of course, difficult to drill a cavity of any size in the back of the central incisor 12. Therefore, a crown linqual mesial cavity 48 can be drilled into the cuspid l6 alone and the bar 50 secured at one end only within the cavity by a suitable filling material, preferably the ADAPTIC (trademark) described above. In this case, the prosthesis 52, shown in broken outline, is supported on the cuspid 16in cantilever beam fashion.

Although the invention has been shown in connection with certain specific embodiments, it will be readily apparent to those skilled in the art that various changes in form, method steps and arrangement of parts can be made to suit requirements without departing from the spirit and scope of the invention. In this respect, it will be appreciated that if the bridge is to replace a cuspid, for example, the cavity will be drilled into the back of the lateral incisor for reception of one end of the spanning bar rather than into the top of the tooth as illustrated in FIGS. 2-5. Aside from this, however, the process is the same.

I claim as my invention:

1. In the method for forming a dental prosthesis, the steps of drilling a cavity into at least one of two teeth separated by a space for at least one missing tooth such that the cavity will have an opening facing the other ofsaid two teeth, inserting an end ofa metallic bar into the thus-formed cavity with the bar spanning the distance between said two teeth, securing an end of said bar within said cavity, filling a hollow tooth form with a pastelike dental restorative material which will harden over a period of time into a mass simulating the appearance of a tooth, forcing said hollow tooth form when filled with the dental restorative material in unhardened paste form down over the portion of said bar spanning the distance between said two teeth such that the material will harden around and become permanently secured to said bar to form a tooth in situ, and thereafter removing from the thus-hardened mass and said spanning bar said hollow tooth form.

2. The method of claim 1 wherein only one cavity is drilled in said two separated teeth, the bar being supported in said one cavity when filled with a dental restorative material in cantilever beam fashion.

3. The method of claim 1 wherein cavities are drilled into both of said two teeth, the cavities facing each other with one cavity being mesial and the other distal, the opposite ends of thebar being inserted into the thus-formed cavities.

4. The method of claim 1 including the step of providing slots in the sides of said hollow tooth form before it is filled with said dental restorative material in paste form such that the tooth form filled with the restorative material may be forced over the bar and into snug-abutting relationship with the 5. The method of claim 1 wherein said end of said bar is secured within said cavity by filling said cavity with a dental restorative material.

6. The method of claim 5 wherein said dental restorative material comprises a resin-bonded quartz composite.

7. Dental bridge comprising a tooth form molded from a resin-bonded quartz composite and having extending through the center of the molded tooth form a bar with at least one end adapted for insertion into a cavity in an adjacent tooth.

8. The dental bridge of claim 7 wherein said bar is provided with radial projections which prevent rotation of said molded tooth form on the bar.

9. The dental bridge of claim 8 wherein said projections are also on the end of said bar inserted into said cavity, and including filling material holding said end within the cavity.

10. The dental bridge of claim 8 wherein said bar is formed from an alloy having as an essential alloying constituent at least one metal selected from the group consisting of platinum, cobalt, chromium, copper, gold, tin and zinc.

11. A spanning bar for holding a dental prosthesis in place between two living teeth comprising a metallic bar formed from material which will not corrode in the mouth and having ends adapted for insertion into cavities drilled into teeth on either side of a space to be occupied by abridge, and radial projections on said bar for preventing rotation of the bar within a filling material inserted into said cavities and surrounding the bar in said space to form a false tooth form.

12. The method of claim 1 including the step of forming on said metallic bar before it is inserted into the thus-formed cavity a plurality of radial projections extending transverse to the bar and substantially along its entire length.

13. A dental prosthesis adapted to be held in place between two living teeth comprising a metallic bar formed from an alloy containing platinum, cobalt and chromium and having ends adapted for insertion into cavities drilled into teeth'on either side of a space to be occupied by a bridge, radial projections extending transverse to and essentially along the entire length of said bar, and a resin bonded quartz composite in the form of a tooth surrounding said bar and permanently bonded thereto. 

1. In the method for forming a dental prosthesis, the steps of Drilling a cavity into at least one of two teeth separated by a space for at least one missing tooth such that the cavity will have an opening facing the other of said two teeth, inserting an end of a metallic bar into the thus-formed cavity with the bar spanning the distance between said two teeth, securing an end of said bar within said cavity, filling a hollow tooth form with a pastelike dental restorative material which will harden over a period of time into a mass simulating the appearance of a tooth, forcing said hollow tooth form when filled with the dental restorative material in unhardened paste form down over the portion of said bar spanning the distance between said two teeth such that the material will harden around and become permanently secured to said bar to form a tooth in situ, and thereafter removing from the thus-hardened mass and said spanning bar said hollow tooth form.
 2. The method of claim 1 wherein only one cavity is drilled in said two separated teeth, the bar being supported in said one cavity when filled with a dental restorative material in cantilever beam fashion.
 3. The method of claim 1 wherein cavities are drilled into both of said two teeth, the cavities facing each other with one cavity being mesial and the other distal, the opposite ends of the bar being inserted into the thus-formed cavities.
 4. The method of claim 1 including the step of providing slots in the sides of said hollow tooth form before it is filled with said dental restorative material in paste form such that the tooth form filled with the restorative material may be forced over the bar and into snug-abutting relationship with the gum.
 5. The method of claim 1 wherein said end of said bar is secured within said cavity by filling said cavity with a dental restorative material.
 6. The method of claim 5 wherein said dental restorative material comprises a resin-bonded quartz composite.
 7. Dental bridge comprising a tooth form molded from a resin-bonded quartz composite and having extending through the center of the molded tooth form a bar with at least one end adapted for insertion into a cavity in an adjacent tooth.
 8. The dental bridge of claim 7 wherein said bar is provided with radial projections which prevent rotation of said molded tooth form on the bar.
 9. The dental bridge of claim 8 wherein said projections are also on the end of said bar inserted into said cavity, and including filling material holding said end within the cavity.
 10. The dental bridge of claim 8 wherein said bar is formed from an alloy having as an essential alloying constituent at least one metal selected from the group consisting of platinum, cobalt, chromium, copper, gold, tin and zinc.
 11. A spanning bar for holding a dental prosthesis in place between two living teeth comprising a metallic bar formed from material which will not corrode in the mouth and having ends adapted for insertion into cavities drilled into teeth on either side of a space to be occupied by a bridge, and radial projections on said bar for preventing rotation of the bar within a filling material inserted into said cavities and surrounding the bar in said space to form a false tooth form.
 12. The method of claim 1 including the step of forming on said metallic bar before it is inserted into the thus-formed cavity a plurality of radial projections extending transverse to the bar and substantially along its entire length.
 13. A dental prosthesis adapted to be held in place between two living teeth comprising a metallic bar formed from an alloy containing platinum, cobalt and chromium and having ends adapted for insertion into cavities drilled into teeth on either side of a space to be occupied by a bridge, radial projections extending transverse to and essentially along the entire length of said bar, and a resin bonded quartz composite in the form of a tooth surrounding said bar and permanently bonded thereto. 